Lindsay Lohan on GMA: I have a half-sister?

Lindsay Lohan’s dad discovered he has a 17-year-old daughter while appearing on a TV talk show this week. And it turns out LiLo herself got the news the same way.

You can’t blame her for not knowing; The Trisha Godard Show is no Maury. Still, Good Morning America host Amy Robach accidentally dropped the truth-bomb on Linds while asking about the long-secret half sister earlier today.

Yes, positive things. Positive and probably well-rehearsed things — things she might have spent several hours, possibly in the company of that newly hired publicist — scripting.

Because apart from that unfortunate dip into Lohan’s troubled, and well-reported, personal life, her appearance on GMA was all about giving Lohan the opportunity to re-iterate what a “great place” she’s in now. That and to understandably pitch her new TV movie, Liz & Dick. (It airs on Lifetime Nov. 25.)

Staying “positive” has been the reason for Lohan’s pull-out from another recent TV engagement. Her rep cancelled a Q&A with 20/20‘s Barbara Walters earlier this month. At issue: Walters may have asked Lohan something “tough,” HuffPo reports. (Acceptable questions likely being: 1) Was it awesome to play Elizabeth Taylor? and 2) Just how awesome was it?)

So yes, Lohan touched on playing the late screen legend during the GMA sitdown. She talked about how she related to the Oscar-winning beauty: “Elizabeth Taylor actually went to her mother a lot. She was really close to her mother, and I’m pretty much the same,” Lohan told Robach. Also: “I think that, and just as Elizabeth Taylor did, there was a time when I was just doing so much work constantly and I kind of had that moment where I was like, ‘Do I really love doing this?’” Lohan said of her acting career. “And stepping back and seeing other people do other movies and then kind of noticing, ‘Wait, that’s what I love to do. I need to get in the right head space and just focus on being on set. That’s what makes me happiest.'”

Acting is also the best way to keep her out of trouble. (That’s not snark. That’s a fact from the mouth of La Lohan.)

Like many noble pursuits, however, it can be a thankless and trying task to keep Lohan on a film project. Liz & Dick‘s executive producer Larry Thompson recently told E! News that hiring Lohan “is not for the faint of heart.” Nothing personal, it seems; he also raved about her performance. “We had serious challenges to deal with due to her probation and her history,” Thompson told E!. “She might be the most insured actress who ever walked on a sound stage. We tried to insure ourselves against things that could and, in fact, did happen.”